In the drilling of oil and/or gas wells, it sometimes becomes necessary to place oil or other hydrocarbons in the drilling fluid for various downhole drilling conditions. When the drill cuttings reach the surface together with the drilling fluid, they are separated by passage over conventional equipments such as shakers. When using drilling fluids which are not based upon oil or other hydrocarbons, the drill cuttings can be disposed of by overboard disposal (if off-shore) or by land fill operation if the drilling is on land. However, if oil or other hydrocarbons are used in the drilling fluid, the hydrocarbon soaked drill cuttings can not be thrown overboard because of environmental pollution. As of the current date, many measures have been proposed, but the only solution used by the drilling industry to date for off-shore drilling is to catch the drill cuttings and by bulk process send the drill cuttings to land for disposal. It is very expensive to send the drill cuttings to land, and many more wells would be drilled if it were economical to drill with an oil-based drilling mud or fluid.
U.S. Pat. No. 3,658,654 is directed to an apparatus for recovering oil from oil shale and similar solid materials. The oil is removed from solids by a simple pyrolysis process, in the presence of hyrogen to prevent the formation of high molecular weight materials. The oil bearing solids are passed through an elongated substantially horizontal pyrolysis vessel having an auger-type conveyor therein. During passage through the pyrolysis vessel, the oil bearing solids are heated, and the heating means may comprise a furnace or electrical heating coils.
U.S. Pat. No. 4,098,648 discloses a rotatably retort tube having an internal helical member which is fixed to the tube so that no relative rotation is possible. The patent is directed to the solvent extraction of tar sands and oil bearing shale materials, and seeks to overcome a problem regarding the removal of residual solvent from the already substantially oil free material, before returning the material to the environment. The patent uses a solvent recovery vessel where the solvent is heated and pumped away, and it is unnecessary to raise the temperature much above 200.degree. F. to effect satisfactory evaporation of the solvent. Induction heating is suggested for the heating of the solvent.
U.S. Pat. No. 1,739,066 discloses a device incorporating a counter rotating auger within a rotating drum. The patented device is primarily intended for mixing together particulate materials such as stockfeed, cement, fertilizers, and the like, and discloses that the counterrotating produces a good mixing effect.
U.S. Pat. No. 4,094,769 discloses an auger/retort system for recovering oil from shale and similar materials. The retort is not rotatable, and may be heated using electrical resistance strip heaters extending longitudinally along the retort. The device is provided with an insulation material which is spaced from and completely surrounds the retort to provide good insulation properties, as well as a safety shield for the strip heaters.
U.S. Pat. Nos. 2,973,312, 3,997,388, and 3,652,447 disclose different methods for heating material in a retort. The first two patents disclose the use of ultrasonic and/or microwave heating, and U.S. Pat. No. 3,652,447 suggests the pyrolytic recovery of oil by the use of pulsed laser beams.
Other patents further illustrating the background of the present invention includes U.S. Pat. Nos. 4,077,868 and 3,616,266.